Methods and equipment for filling and sealing gable top cardboard cartons with milk, fruit juice and other various liquid food products are well-known. In filling the cartons, the erected cartons are typically transported along a conveyor line from station-to-station. The liquid filling machines have at least two or more stations at which a predetermined amount of the liquid is dispensed at a high rate into the open top of the carton to fill the carton. In the case where there are two stations, typically half the liquid is dispensed at the first station, and the other half of the liquid is dispensed at the second station. After the carton has been filled at the second or final station, the carton is transported along the conveyor to another series of stations where the gable top is formed and sealed. The carton is typically polyethylene coated, so that the sealing of the gable top is done with a combination of heat and pressure.
These liquid filling machines operate at a high production rate, and, therefore, the liquid must be dispensed into the carton rapidly. When the liquid is rapidly discharged into the carton, a foam develops on and over the surface of the liquid. The amount of foam produced during filling depends upon the type of liquid and rate in which the fluid is dispensed from a dispensing nozzle and the particular configuration of the dispensing nozzle. Some configurations of nozzles have more problems than others with foam. However, all dispensing nozzles form some foam within the carton on the surface of the liquid.
The foam becomes a problem when trying to seal a gable top carton or any carton using an adhesive that must be heated before adhesion occurs. The foam can prevent the adhesive from adhering and prevent the gable top from being properly sealed. It is necessary, therefore, to remove excess foam after filling the carton. In the past, a variety of methods have been developed in trying to eliminate the foam within the carton.
One method has been to use a vacuum device, which sucks the foam out of the carton. The vacuum also tends to draw whatever dust, bacteria and other particles that are present in the air over the surface of the liquid food product into the carton. Contamination of the liquid food product as a result of the defoaming process can be a significant problem.
Rydell in U.S. Pat. Nos. 2,792,029 and 2,796,894 shows a tubular vacuum defoamer for milk filling machines. Rydell '029 Patent further includes a beater having blades positioned in the vacuum stream. The beater causes the foam to be directed out on the side wall of the tube so that it is returned to a liquid form and back into the container.
Ward in U.S. Pat. No. 2,753,098 describes another vacuum milk defoaming device wherein the foam is removed by a vacuum defoamer which includes a plate that covers the top of the open container and a vacuum line extending through the plate to suck foam out of the container. The device of the Ward Patent uses a plate to cover the top of the container. In a high production type filling machine, openings between the plate 26 and the top of the container allow dust, bacteria and other particles to be drawn near the surface of the liquid food product in the container.
Burger et al in U.S. Pat. No. 3,169,561 describes an elastic wave generator which directs elastic waves onto the surface of the liquid in the container to break up the foam.
Ullman et al in U.S. Pat. No. 2,752,083 and Wollenwever in U.S. Pat. No. 2,328,372 use a gas that is directed onto the foam to break up the foam. Ullman et al shows a defoaming arrangement in which a high pressure gas, such as air or steam, is directed in a jet onto the surface of the liquid in the carton to break up the foam. Gas nozzles are positioned between liquid discharge nozzles which fill the carton at successive stations. Wollenwever describes the use of a heated gas, specifically steam, which is blown onto the surface of the liquid to break up the foam.
Andre in U.S. Pat. No. 2,604,247 also uses steam which is discharged from a nozzle to assist in removing foam in cooperation with a suction pipe.
McKinnis in U.S. Pat. No. 2,377,796 includes a machine which fills containers with an oxidizable liquid, such as fruit and vegetable juices. Atmospheric air is purged from the container by a jet of inert gas or steam. When the juice is introduced into the container, it is surrounded by a protective blanket of inert gas or steam.